27 February 2019 News

FarFarOut beats FarOut as most distant Solar System body ever seen

Artist’s illustration of a distant Kuiper Belt object in the dim outer reaches of our solar system. Image: ASA/ESA/G. Bacon (STScI)]
Artist’s illustration of a distant Kuiper Belt object in the dim outer reaches of our solar system. Image: ASA/ESA/G. Bacon (STScI)]

Farout, the farthest known minor ice body found bobbing around in the outer fringes of the Solar System by Dr. Scott Sheppard and his colleagues last year is no longer the most distant object known about; it has been surpassed by FarFarOut – a newly discovered extreme Trans-Neptunian Object (eTNO) that is 140 AU away.

The outer realm of the Solar System is a vast, chaotic and relatively little-known about domain, that is proving to be just as interesting as the space closer to us. Hoping to understand more about this beguiling remote region and why the trajectories of some small ice bodies behave the way they do, is a small team of scientists who are on a mission to catalogue the most far-flung objects still bound, in some shape or form, to the Sun.

Headed by Dr Sheppard, the team famously found The Goblin in October 2018. So called because it was discovered around Halloween, this 300 kilometre wide object was discovered about 80 AU from the Sun; an astronomical unit is the mean distance from the centre of the earth to the centre of the sun - so around 149.6 million kilometres. Neptune for comparison is 30 AU away, which equates to roughly 4.5 billion kilometres.

The team then found Farout, a minor planet whose official name is 2018 VG18, a month later in November. Spotted a whopping 120 AU away, it was first discovered by researchers using the Subaru 8-meter telescope in Hawaii and later confirmed using the Magellan telescope at Las Campanas Observatory in Chile.

Finding odd-ball ice worlds appears to have become something of a successful sideline for Sheppard and his team, even though it was something much bigger that they initially had their sights set on. Inspired by the odd orbits of objects such as 2012VP113 and Sedna, the team has long suspected that a mysterious Planet Nine lay hidden in the far reaches of the Solar System and was causing a group of outliers to bunch-up their orbits in a similar direction.

Objects such as Sedna are confined to a region known as no-man’s land and never come in close enough to giant planets like Neptune, Uranus and Jupiter, to have significant gravitational interactions with them. These far-flung balls of water-ice can therefore be good probes of what is happening in the Solar System's outer reaches.

However, it is hard to put forward theories when only a few objects are known about. Up until around 2012 many believed that the outliers formed in the Sun’s birth cluster when the Sun was still forming. The gravitational forces exerted from these close-in, evolving stars was enough to de-couple their orbits and pull them away from the rest of the icy bodies strewn in disks around the Sun such as the Kuiper belt.

Now, with more and more objects being found by Sheppard and team, eventually the numbers may add up to prove or disprove the existence of Planet Nine; a proposed unseen disrupter suspected to be around three times as big as Earth.

Amazingly, this new discovery was found by Sheppard because of snow putting his plans on hold for the day. With nothing better to do, he put his time to good use, trawled through data and found FarFarOut, said Sheppard where he revealed this ‘hot off the press’ discovery in a recent public lecture held at the Carnegie Institution for Science in Washington last week.

Like Farout, not a lot is known about FarFarOut other than it is very, very faint. It is on the edge of our ability to see it, said Sheppard and will take a year or two of processing to work out further intrinsic details about the small-ice world. Some of that work will start next week when Sheppard and team hope to re-observe the object.

As such, there is a good chance that before more is discovered about the farthest known object in our Solar System, that FarFarFarOut and possibly FarFarFarFarOut will also have been found by then.

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